The subject matter described herein relates to surface inspection techniques, and more particularly to detecting surface pits such as, for example surface pits in a semiconductor material or in the epitaxial layer which has been deposited upon a semiconductor material.
Manufacturers of light-emitting diodes (LEDs) and other types of optoelectronic integrated circuits (ICs) grow or deposit multiple epitaxial layers on transparent or non transparent substrates, including for example sapphire and silicon carbide. Small pits, e.g., on the order of 0.2 micrometers (μm) to 2 μm in diameter can cause reductions in yield and device performance.
Semiconductor substrates such as, for example, sapphire and silicon carbide may or may not have epitaxial layers deposited upon them to produce LEDs and other types of optoelectronic integrated circuits (ICs). These substrates and or their epitaxial layers may be inspected for defects such as, e.g., surface imperfections, particles, irregularities in the thickness of thin film coatings, and the like, which may hamper the performance of the semiconductor material. Some existing inspection systems direct a beam of radiation on the surface of the semiconductor material, then collect and analyze light reflected and/or scattered from the surface to quantify characteristics of the surface. Additional inspection techniques are desirable. In particular, it is desirable to inspect EPI (epitaxial) layers for defects such as scratches, pits, particles and other defects.